1. Field of the Invention
The present invention relates to a method for assembling parts and more particularly to a method for fixing with adhesive a part and a part support for mounting the part via an intermediate member or members provided between the part and the part support.
2. Description of the Related Art
Generally, to fix a part and a part support via a bracket-like intermediate member positioned between the part and the part support, it has been customary to fasten the part and part support and the intermediate member by using screws. Screws, however, are apt to displace the part relative to the part support due to a torque when they are driven, and thereby make it difficult to accurately position the part.
In light of the above, the part and part support and the intermediate member may be so configured as to mate with each other in a preselected positional relation. Although this approach enhances the positional accuracy of the individual structural element, it causes the positional accuracy of the resulting assembly to be unconditionally determined by the finishing accuracy of the individual element. It is therefore necessary to machine the individual structural element with high accuracy. While this kind of approach reduces the assembling cost, it increases the material and machining costs of the individual structural element. This is particularly true when the parts are plastic moldings apt to scatter in accuracy due to sinking and other causes.
To assemble the part and part support via the intermediate member without being effected by the finishing accuracy of the individual element while maintaining them in an accurate positional accuracy, it is desirable to connect the part, part support and intermediate member by using adhesive. This, however, brings about a problem that whether or not the part and part support are dislocated at the time of adhesion determines the positioning accuracy of the part relative to the part support after adhesion. It follows that the positional relation between the part and the part support at the time of adhesion has critical influence on the quality of the resulting product.
For example, assume that the above part is a print head included in a printer, a line sensor included in a scanner, or a solid imaging device included in a CCD (Charge Coupled Device) camera. Then, when any positional error occurs between the part and the part support, it displaces an image printed or read by the part and thereby deteriorates image quality.
Particularly, when the part is an ink jet head included in an ink jet printer, it occurs that the distance between the head surface of the head formed with nozzle holes and a recording medium is scattered or that the nozzle holes fail to accurately face a position where an image should be printed on the recording medium. As a result, ink drops ejected from the nozzle holes reach the recording medium outside of a preselected printing position, noticeably lowering the image quality. In the case of a color printer including heads respectively loaded with ink of different colors (usually yellow ink, magenta ink, cyan ink and black ink), any positional error between the heads makes the print positions of ink drops of different colors irregular. This brings the different colors forming a color image out of register or causes the color image to distort.
The prerequisite with the adhesive scheme is therefore that the part and the part support be accurately held, beforehand, in a preselected positional which will allow the part and part support to accurately face an assembly position at the time of adhesion. In this connection, in the case of the head of a color printer, the allowable error of the head adhered to the part support should be confined in the range of the order of microns.
As for the adhesive scheme, the positional relation between the part and the part support at the time of adhesion is a critical factor that determines the accuracy of mounting of the part to the part support, as stated earlier.
It has been customary with a method and an apparatus for assembling, e.g., the head of an ink jet printer to use a CCD camera including a solid imaging device. The CCD camera picks up the nozzle hole formed in the head surface in the direction perpendicular to the head surface. A computing section computes the position of the center of gravity of the resulting image and thereby measures the positions of the head in the directions of X and Y axes. At the same time, a control and operation unit calculates the position of the head in the direction of the Z axis on the basis of data output from an autofocus device included in the camera and relating to the amount of defocus in the Z axis direction. The head surface and nozzle hole are adjusted in position relative to the part support on the basis of the result of measurement.
The above conventional CCD camera scheme has the following problem left unsolved. Assume that the camera is focused on a single nozzle hole formed in the head surface for measurement. Then, the positions of the nozzle hole in the X, Y and Z axis directions can be accurately determined. However, it is impossible to accurately measure, based on the positions of the single nozzle, the deviation of the other nozzles holes ascribable to the irregularity or the rotation of the head surface. It is therefore extremely difficult to correct such deviation of the other nozzles on the basis of the positions of the single nozzle hole. Consequently, a long period of time and sophisticated calculations are necessary for the head to be positioned, obstructing rapid head assembly and simple measurement.
Another conventional method and apparatus for connecting the part, part support and intermediate member uses three different chucks. A first chuck holds the part support and locates it at a preselected assembly position. A second chuck holds the part in a position adjustable relative to the part support. The position of the part is varied while being monitored via a CCD camera in order to adjust it relative to the part support at the assembly position. As a result, the part and part support are accurately positioned relative to each other. After a third chuck has located the intermediate member between the part and the part support, the intermediate member and the part and part support are adhered together.
However, the prerequisite with the above chuck scheme is that the chucks, a measuring unit included in the COD camera and an adhesive applying unit be prevented from interfering with each other. To meet this requirement, each of the chucks and various units needs a complicated structure and must be controlled in an extremely sophisticated way. Moreover, the layout of the chucks and units are severely limited.
Further, to reduce the overall size of the unit made up of the intermediate member, part and part support, the intermediate member should preferably be reduced in size as far as possible. Assume that the third chuck is so configured as to hold such a small intermediate member with mechanical holding means. Then, it is necessary to adjust the force of the holding means and to control a holding portion included in the holding means with utmost accuracy, so that the intermediate member will not be damaged or will not slip out of the chuck.
Particularly, assume that the unit includes a plurality of intermediate members supporting a single part. Then, to hold the intermediate members by using the above mechanical holding means and move them to a preselected mounting position at the same time, the chuck must have its construction complicated to a noticeable degree. Further, assume that adhesive applying means applies adhesive to the expected surfaces of the intermediate members being held by the holding means. Then it is likely that the adhesive feed portion of the adhesive applying means contacts the surfaces of the intermediate members held by the holding means and dislocates them.
As stated above, the apparatus of the type holding the intermediate member or members with mechanical holding means needs more complicated adjustment, control and construction and results in a greater size as the size of the individual intermediate member decreases or as the number of the intermediate members increase.
It is therefore an object of the present invention to provide a method and an apparatus capable of assembling parts while easily and accurately maintaining intermediate members in a positional relation for adhesion relative to a part and a part support.
It is another object of the present invention to provide a method and an apparatus capable of assembling a part, a part support and intermediate members with a simple construction.
It is a further object of the present invention to provide a method and an apparatus capable of assembling parts while conveying intermediate members relative to a part and a part substrate with simple and easy holding and conveying means.
In accordance with the present invention, a method of assembling a part and a part support by use of adhesive via an intermediate member provided between the part and the part support includes the steps of positioning and holding the part support at a preselected assembling position, and varying, while holding the part in a position adjustable relative to the part support, the position of the part and detecting three preselected points of the part to thereby adjust the position in which the part is to be mounted to the part support.
Also, in accordance with the present invention, an apparatus for assembling a part and a part support by use of adhesive via an intermediate member provided between the part and the part support includes a part support holding portion for positioning and holding the part support at a preselected assembling position. A part supporting portion supports the part in a position variable relative to the part support held by the part support holding portion. A part position detecting section detects preselected three points of the part supported by the part supporting portion. A part position adjusting section adjusts, based on the positions of the three detected points, the position of the part relative to the part support.
Further, in accordance with the present invention, a method of assembling a part and a part support by use of adhesive via an intermediate member provided between the part and the part support beging with the step of preparing a jig. The jig includes a part support holding portion for positioning and holding the part support such that the part support remains in an assembly position and maintains portions thereof for mounting the part and intermediate member open, a part supporting portion for supporting the part in such a manner as to secure a region for adjusting the position of the part relative to the part support positioned on the part support holding portion, and an intermediate member supporting portion for supporting the intermediate member in a position ready to be mounted to the part support positioned on the part supporting holding portion. The part, part support member and intermediate member are mounted to the jig. The position of the part is adjusted relative to the part support, and the intermediate member is mounted after the jig has been positioned at a preselected assembling position.
Furthermore, in accordance with the present invention, an apparatus for assembling a part and a part support by use of adhesive via an intermediate member provided between the part and the part support includes a jig. The jig includes a part support holding portion for positioning and holding the part support such that the part support remains in an assembly position and maintains portions thereof for mounting the part and intermediate member open, a part supporting portion for supporting the part in, such a manner as to secure a region for adjusting the position of the part relative to the part support positioned on the part support holding portion, and an intermediate member supporting portion for supporting the intermediate member in a position ready to be mounted to the part support positioned on the part supporting holding portion. A jig positioning device positions at a preselected assembly position the jig loaded with the part, part support member and intermediate member in the part supporting portion, part support holding portion and intermediate member supporting portion, respectively.
Moreover, in accordance with the present invention, in a part assembling apparatus including a holding and conveying device for holding an intermediate member expected to fix a part and a part support via adhesive and conveying the intermediate member to a preselected mounting position between the part and the part support, the holding and conveying device comprises an air chuck for retaining the intermediate member thereon by vacuum.